1. Field of the Invention
The present invention relates to environmental stress-inducible 996 promoter isolated from rice and use thereof. Specifically, the present invention relates to environmental stress-inducible 996 promoter isolated from rice, a recombinant plant expression vector comprising said promoter, a method of producing a target protein by using said recombinant plant expression vector, a method of producing a transgenic plant using said recombinant plant expression vector, a transgenic plant produced by said method, a method of improving resistance of a plant to environmental stress by using said promoter, and a primer set for amplification of said promoter.
2. Description of the Related Art
A promoter is a part of genome which is located upstream of a structural gene and regulates transcription of the structural gene into mRNA. A promoter is activated by binding of various general transcription factors, and it typically comprises a base sequence such as TATA box, CAT box, etc. which regulates gene expression. Since proteins that are required for basic metabolism of a living body need to be maintained at constant concentration, a promoter that is associated with genes of such proteins is constantly activated even by general transcription factors only. On the other hand, for the proteins of which function is not required during normal time but required only under specific circumstances, an inducible promoter which can induce expression of a corresponding structural gene is linked to the corresponding genes. In other words, an inducible promoter is activated by binding of specific transcription factors that are stimulated during a developmental process of an organism or stimulated by environmental factors.
For the development of a transgenic plant based on gene transformation, a promoter which can induce constant and strong expression, for example cauliflower mosaic virus 35S promoter (CaMV35S, Odell et al., Nature 313: 810-812, 1985), is widely used. However, since constant overexpression of a specific gene linked to such promoter can produce an excess amount of proteins that are not necessarily required for metabolism of a normal living body, it often becomes problematic in that a transgenic plant does not properly germinate or only a small-sized plant is produced due to toxic effect generated by the proteins present in an excess amount. As a representative example, it was found that Arabidopsis thaliana in which DREB1A, a gene encoding transcription factors responding to environmental stress, is overexpressed by using CaMV35S promoter has improved resistance to low temperature and drought condition, but also had a dwarfed phenotype with inhibited growth and increased production of proline and water-soluble carbohydrates (Liu et al., Plant Cell 10: 1391-1406, 1998; Gilmour et al., Plant Physiol. 124: 1854-1865, 2000). Occurrence of such problems can be minimized by using an inducible promoter for rd29A, that is a gene relating to environmental stress, instead of CaMV35S promoter (Kasuga et al, Nat. Biotechnol. 17: 287-291, 1999).
Under the circumstances, instead of a promoter which constantly induces gene expression in a plant tissue, an inducible promoter which can induce expression of a target gene at specific time and under specific condition has been actively studied and developed. As a scientific research, an inducible promoter system, which can stimulate biosynthesis of a target protein based on introduction of a promoter isolated from a microorganism or an animal to a plant and use of a chemical substance as an inducing agent, has been widely developed. Until now, as an example of application of an expression inducing system based on use of a chemical substance on a plant, a method in which a steroid such as dexamethasone, antibiotics such as tetracycline, and a chemical substance such as copper ion, IPTG and the like are used as an inducing agent has been known (Gatz et al., Plant J. 2: 397-404, 1992; Weimann et al., Plant J. 5: 559-569, 1994; Aoyama T. and Chua N-H, Plant J. 11: 605-612, 1997). However, such method is problematic in that the chemical substance used as an inducing agent for a system is extremely expensive and such chemicals often have a toxic effect by themselves, so that the method cannot be applied to all plants.
In Korean Patent Registration No. 10-0781059, an inducible promoter that is activated by environmental stress and a method of obtaining a transgenic protein in guard cells by using such promoter are described. In addition, in Korean Patent Registration No. 10-0578461, a stress-inducible promoter that is isolated from rice is disclosed. However, these are all different from the promoter described in the present invention.
The present invention was devised in view of above-described needs. Specifically, after intensive studies to develop a promoter which is induced by environmental stress, particularly by drought stress, inventors of the present invention found that a certain promoter isolated from rice is strongly induced by drought stress, and therefore completed the present invention.